Akinori Fukushima

Role of an Aluminum Atom on Graphene for Hydrogen Adsorption

The effects of an aluminum atom on the hydrogen adsorption onto graphene are investigated. An aluminum atom can be attached on a graphene sheet by a bond with both covalent and ionic properties. Then, the electric charge is transferred from the aluminum atom to the graphene. The activation energy for the hydrogen adsorption is significantly lowered by the addition of the aluminum atom for both atomic and molecular adsorptions. The hydrogen adsorption energy is also lowered significantly by the aluminum atom.

Theoretical study of adsorption of lithium atom on carbon nanotube

We investigate the adsorption of lithium atoms on the surface of the (12,0) single wall carbon nanotube (SWCNT) by using ab initio quantum chemical calculations. The adsorption of one lithium atom on the inside of this SWCNT is favored compared to the outside. We check this feature by charge transfer and regional chemical potential density. The adsorption of multiple lithium atoms on the interior of the SWCNT is studied in terms of adsorption energy and charge transfer. We show that repulsive force between lithium atoms destabilizes a system for the large number of lithium atoms.

A Theoretical Study on a Reaction of Iron(III) Hydroxide with Boron Trichloride by Ab Initio Calculation

Abstract We investigate a reaction of boron trichloride ( BCl 3 ) with iron(III) hydroxide ( Fe ( OH ) 3 ) by ab initio quantum chemical calculation as a simple model for a reaction of iron impurities in BCl 3 gas. We also examine a reaction with water. We find that compounds such as Fe ( Cl ) ( OBCl 2 ) 2 ( OHBCl 2 ) and Fe ( Cl ) 2 ( OBCl 2 ) ( OHBCl 2 ) are formed while producing HCl and reaction paths to them are revealed. We also analyze the stabilization mechanism of these paths using newly-developed interaction energy density derived from electronic stress tensor in the framework of the Regional DFT (Density Functional Theory) and Rigged QED (Quantum ElectroDynamics).

Calculation of the Electronic State in Electronic Current for Nanowire Models

The first results of the calculations of our program code are shown for nanowire models. In our code, the electronic current is treated as quantum states, and the effects of the coulomb and exchange interaction by conductive electrons on electrons in system are included. We show our results as the local electronic current density defined by one of the authors. The magnetic field induced by the electronic current is studied by including effects of vector potential in electronic state calculations. The effects on the electrons in systems by the conductive electrons are also studied. By the existence of the conductive electrons in the systems, the energy eigenvalues of higher orbitals rise, while the lower orbitals are stabilized by the conductive states. It may imply that materials is made more conductive by conductive electrons since the electons in the materials are unstabilized by them.

Local Dielectric Property of Hafnium and Lanthanum Atoms in HfLaOx

In this work, we investigate the electronic contribution to local dielectric property of La2O3 and HfO2 using cluster models. The relation between the coordinate number of metal atoms and their bonding energy shows a hint that hafnia takes the cubic structure by the incorporation of La2O3 in HfO2. The local properties of polarizability and dielectric constant of La2O3 and HfO2 are closely similar to each other. It is considered to be one of the reasons why the incorporation of lanthanum atoms does not lower the permittivity of HfO2. We confirm this by the study of the local dielectric property of the HfLaOx cluster model. We compare the dielectric properties around an oxygen atom and that between the oxygen atom and a next metal atom. Our results show that the contribution to the dielectric response from the bond regions is not so large.

Local Dielectric Property of Cubic Hafnia

The dielectric property of the cubic hafnia is investigated in terms of the polarizability density and the dielectric constant density defined by one of the authors. We study it by using the cluster model embedded in point charges which represent the surrounding atoms. It is shown that the cubic hafnia show complicated responses to external electric fields, in particular, rotational ones. We stress that the nanosize material should be studied in the local and tensor quantity analysis to describe rotational responses correctly. We also show that the choice of models, in particular, termination condition, is important for these analyses, by comparing the point charge model and the hydrogen termination model.

Local Dielectric Property of Cubic, Tetragonal, and Monoclinic Hafnium Oxides

We investigate the electronic contribution to local dielectric property in terms of the local polarizability density and dielectric constant density, for the cubic, tetragonal, and monoclinic structure of HfO2 and compare their dielectric properties with those of SiO2. We show appropriate termination conditions of our cluster models to realize the condensed property of dielectric; point charge conditions for HfO2 whose bond is ionic, while hydrogen termination conditions for SiO2 whose bond has covalent property. We show that local parts of materials have complicated responses to external electric fields, in particular, rotational ones. Hence, nanosize materials should be studied in the local and tensor quantity analysis to describe rotational responses correctly. It is clarified that the electronic contribution to local polarizability and dielectric constant densities is almost independent of the structures of HfO2 crystals. We show that the electronic contribution to dielectric response of HfO2 is significantly large compared to those of SiO2. In addition, it is found that the average value of dielectric constant around O atoms is larger than other regions in both HfO2 and SiO2.